/*
 * contrib/btree_gist/btree_uuid.c
 */
#include "postgres.h"

#include "btree_gist.h"
#include "btree_utils_num.h"
#include "port/pg_bswap.h"
#include "utils/uuid.h"

typedef struct
{
    pg_uuid_t    lower,
                upper;
} uuidKEY;


/*
 * UUID ops
 */
PG_FUNCTION_INFO_V1(gbt_uuid_compress);
PG_FUNCTION_INFO_V1(gbt_uuid_fetch);
PG_FUNCTION_INFO_V1(gbt_uuid_union);
PG_FUNCTION_INFO_V1(gbt_uuid_picksplit);
PG_FUNCTION_INFO_V1(gbt_uuid_consistent);
PG_FUNCTION_INFO_V1(gbt_uuid_penalty);
PG_FUNCTION_INFO_V1(gbt_uuid_same);


static int
uuid_internal_cmp(const pg_uuid_t *arg1, const pg_uuid_t *arg2)
{
    return memcmp(arg1->data, arg2->data, UUID_LEN);
}

static bool
gbt_uuidgt(const void *a, const void *b, FmgrInfo *flinfo)
{
    return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) > 0;
}

static bool
gbt_uuidge(const void *a, const void *b, FmgrInfo *flinfo)
{
    return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) >= 0;
}

static bool
gbt_uuideq(const void *a, const void *b, FmgrInfo *flinfo)
{
    return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) == 0;
}

static bool
gbt_uuidle(const void *a, const void *b, FmgrInfo *flinfo)
{
    return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) <= 0;
}

static bool
gbt_uuidlt(const void *a, const void *b, FmgrInfo *flinfo)
{
    return uuid_internal_cmp((const pg_uuid_t *) a, (const pg_uuid_t *) b) < 0;
}

static int
gbt_uuidkey_cmp(const void *a, const void *b, FmgrInfo *flinfo)
{
    uuidKEY    *ia = (uuidKEY *) (((const Nsrt *) a)->t);
    uuidKEY    *ib = (uuidKEY *) (((const Nsrt *) b)->t);
    int            res;

    res = uuid_internal_cmp(&ia->lower, &ib->lower);
    if (res == 0)
        res = uuid_internal_cmp(&ia->upper, &ib->upper);
    return res;
}


static const gbtree_ninfo tinfo =
{
    gbt_t_uuid,
    UUID_LEN,
    32,                            /* sizeof(gbtreekey32) */
    gbt_uuidgt,
    gbt_uuidge,
    gbt_uuideq,
    gbt_uuidle,
    gbt_uuidlt,
    gbt_uuidkey_cmp,
    NULL
};


/**************************************************
 * uuid ops
 **************************************************/


Datum
gbt_uuid_compress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *retval;

    if (entry->leafkey)
    {
        char       *r = (char *) palloc(2 * UUID_LEN);
        pg_uuid_t  *key = DatumGetUUIDP(entry->key);

        retval = palloc(sizeof(GISTENTRY));

        memcpy((void *) r, (void *) key, UUID_LEN);
        memcpy((void *) (r + UUID_LEN), (void *) key, UUID_LEN);
        gistentryinit(*retval, PointerGetDatum(r),
                      entry->rel, entry->page,
                      entry->offset, FALSE);
    }
    else
        retval = entry;

    PG_RETURN_POINTER(retval);
}

Datum
gbt_uuid_fetch(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);

    PG_RETURN_POINTER(gbt_num_fetch(entry, &tinfo));
}

Datum
gbt_uuid_consistent(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    pg_uuid_t  *query = PG_GETARG_UUID_P(1);
    StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);

    /* Oid        subtype = PG_GETARG_OID(3); */
    bool       *recheck = (bool *) PG_GETARG_POINTER(4);
    uuidKEY    *kkk = (uuidKEY *) DatumGetPointer(entry->key);
    GBT_NUMKEY_R key;

    /* All cases served by this function are exact */
    *recheck = false;

    key.lower = (GBT_NUMKEY *) &kkk->lower;
    key.upper = (GBT_NUMKEY *) &kkk->upper;

    PG_RETURN_BOOL(
                   gbt_num_consistent(&key, (void *) query, &strategy,
                                      GIST_LEAF(entry), &tinfo, fcinfo->flinfo)
        );
}

Datum
gbt_uuid_union(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    void       *out = palloc(sizeof(uuidKEY));

    *(int *) PG_GETARG_POINTER(1) = sizeof(uuidKEY);
    PG_RETURN_POINTER(gbt_num_union((void *) out, entryvec, &tinfo, fcinfo->flinfo));
}

/*
 * Convert a uuid to a "double" value for estimating sizes of ranges.
 */
static double
uuid_2_double(const pg_uuid_t *u)
{
    uint64        uu[2];
    const double two64 = 18446744073709551616.0;    /* 2^64 */

    /* Source data may not be suitably aligned, so copy */
    memcpy(uu, u->data, UUID_LEN);

    /*
     * uuid values should be considered as big-endian numbers, since that
     * corresponds to how memcmp will compare them.  On a little-endian
     * machine, byte-swap each half so we can use native uint64 arithmetic.
     */
#ifndef WORDS_BIGENDIAN
    uu[0] = BSWAP64(uu[0]);
    uu[1] = BSWAP64(uu[1]);
#endif

    /*
     * 2^128 is about 3.4e38, which in theory could exceed the range of
     * "double" (POSIX only requires 1e37).  To avoid any risk of overflow,
     * put the decimal point between the two halves rather than treating the
     * uuid value as a 128-bit integer.
     */
    return (double) uu[0] + (double) uu[1] / two64;
}

Datum
gbt_uuid_penalty(PG_FUNCTION_ARGS)
{
    uuidKEY    *origentry = (uuidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(0))->key);
    uuidKEY    *newentry = (uuidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(1))->key);
    float       *result = (float *) PG_GETARG_POINTER(2);
    double        olower,
                oupper,
                nlower,
                nupper;

    olower = uuid_2_double(&origentry->lower);
    oupper = uuid_2_double(&origentry->upper);
    nlower = uuid_2_double(&newentry->lower);
    nupper = uuid_2_double(&newentry->upper);

    penalty_num(result, olower, oupper, nlower, nupper);

    PG_RETURN_POINTER(result);
}

Datum
gbt_uuid_picksplit(PG_FUNCTION_ARGS)
{
    PG_RETURN_POINTER(gbt_num_picksplit(
                                        (GistEntryVector *) PG_GETARG_POINTER(0),
                                        (GIST_SPLITVEC *) PG_GETARG_POINTER(1),
                                        &tinfo, fcinfo->flinfo
                                        ));
}

Datum
gbt_uuid_same(PG_FUNCTION_ARGS)
{
    uuidKEY    *b1 = (uuidKEY *) PG_GETARG_POINTER(0);
    uuidKEY    *b2 = (uuidKEY *) PG_GETARG_POINTER(1);
    bool       *result = (bool *) PG_GETARG_POINTER(2);

    *result = gbt_num_same((void *) b1, (void *) b2, &tinfo, fcinfo->flinfo);
    PG_RETURN_POINTER(result);
}
